Rinse sushi rice under cold water until clear. Cook with water in a pot. Simmer gently for 15 minutes. Mix rice vinegar, sugar and salt separately. Fold mixture into warm rice carefully. Let cool.

Cut chicken breasts into long strips. Season lightly with salt and pepper. Keep pieces even in size. This helps them cook evenly and fit nicely inside the sushi rolls.

In a bowl, whisk egg with cold water. Add flour slowly and mix lightly. Do not overmix. The batter should be slightly lumpy for a light and crispy coating.

Dip chicken strips into tempura batter first. Then roll them in panko breadcrumbs for extra crunch. Fry in hot oil until golden brown and cooked through. Drain on paper towels.

Place bamboo mat on a flat surface. Cover with plastic wrap. Lay one nori sheet shiny side down. Spread a thin layer of sushi rice evenly, leaving one inch empty at the top.

Place one or two crispy chicken strips in the center. Add cucumber and avocado slices next to the chicken. Do not overfill. This makes rolling easier and keeps shape neat.

Lift the bamboo mat gently. Roll tightly from the bottom. Press lightly to shape into a firm log. Seal the edge with a little water to keep roll closed.

Use a sharp knife dipped in water. Cut roll into six equal pieces. Wipe knife between cuts for clean slices. Serve with soy sauce, ginger and wasabi if desired.